In the past, materials such as plastic, metal, paper, wood, fiber, leather, glass, rubber, ceramic, concrete and asphalt have been used in a variety of industrial products. Most of the industrial products are comprised of composite materials, which are obtained by combining more than two different materials. The use of composite materials enables high functionalization and cost reduction. The coating materials for such composite materials require coating property and adhesiveness to different materials.
In response to such demand, coating materials that include propylene polymer which is graft-modified using maleic anhydride with enhanced adhesiveness to polyolefin-based molded articles (Patent Literature (hereinafter, referred to as “PTL”) 1), and coating materials with improved coating property that include a polymer obtained by chlorinating an acid-modified propylene polymer and reacting the chlorinated acid-modified propylene polymer with an epoxy compound (PTL 2), have been manufactured.
However, the above-mentioned coating materials required processes, such as, heating above the melting point of a resin during coating process, which resin is included in the coating material, and drying the coating film for a long time for stabilization. Hence, further improvements are being required for such coating materials.
Meanwhile, it is also required to make the drying process efficient; that is to say, increasing the concentration of resin within the coating material for the purpose of reducing the time taken for drying and the related energy cost. However, there have been cases wherein higher resin concentrations increase the viscosity and lower handling property of the coating material. In other cases, misting, streak and unevenness appeared during the coating process, or preservation stability of coating material is undermined. In this regard, the enhancement of solubility of resin in solvent to solve the above-mentioned problems is being studied. For example, a coating material is disclosed of which propylene elastomer, which is graft-modified with a polar monomer, is dissolved or dispersed in an organic solvent (PTL 3).